Blood pressure is one index for analyzing cardiovascular disease, and performing a risk analysis based on blood pressure is effective in preventing cardiovascular-related conditions such as stroke, heart failure, and myocardial infarction. Thus far, diagnoses have been made using blood pressure (casual blood pressure) measured at medical institutions, such as during hospital visits, health checkups, and so on. However, recent research has shown that blood pressure measured at home (home blood pressure) is more useful in diagnosing cardiovascular disease than casual blood pressure. As a result, blood pressure meters for use at home are becoming widespread.
Many household blood pressure meters employ an oscillometric blood pressure measurement technique. When measuring blood pressure using the oscillometric technique, a cuff is wrapped around a measurement area such as an upper atm, the cuff is inflated until the internal pressure thereof (a cuff pressure) reaches a pressure higher than a systolic blood pressure by a predetermined pressure (for example, 30 mmHg), and the cuff pressure is then reduced gradually or in steps. As the pressure is being reduced, a change in the volume of the artery is detected as a change in the pressure superimposed on the cuff pressure (a pulse wave amplitude), and the systolic blood pressure and diastolic blood pressure are determined based on the change in the pulse wave amplitude. Furthermore, with the oscillometric technique, it is possible to measure the blood pressure by detecting a pulse wave amplitude occurring while the cuff pressure is being increased.
To accurately detect the pulse wave amplitude in such blood pressure measurements, it is necessary to increase or decrease the cuff pressure at a constant speed using a pump or a valve. Specifically, feedback control is executed on a driving voltage for a pump or a valve during constant speed inflation control or constant speed deflation control based on a difference between an average speed and a target speed, so that the average speed reaches the target speed. A pump that uses a motor as its driving source, a piezoelectric micro pump that uses a piezoelectric element as its driving source, or the like can be employed as blood pressure measurement pump that undergoes feedback control. Patent Literature 1 (JP 2009-74418A), for example, discloses a piezoelectric micro pump structure.
Meanwhile, Patent Literature 2 (JP H5-42114A) discloses a method for determining an inflation speed based on a cell voltage as a method for determining a pump inflation speed.